In conventional prior art four-stroke internal combustion engines, the mutual angular relationships of the crankshaft, camshaft, and valves are mechanically fixed; that is, the valves are opened and closed fully and identically with every two revolutions of the crankshaft, fuel/air mixture is drawn into each cylinder in a predetermined sequence, ignited by the sparking plug, and the burned residue discharged. This sequence occurs irrespective of the rotational speed of the engine or the load being placed on the engine at any given time.
It is known that for much of the operating life of a multiple-cylinder engine, the load might be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency could be improved if one or more cylinders of a larger engine could be withdrawn from firing service. It is known in the art to accomplish this by de-activating the valve train leading to pre-selected cylinders in any of various ways, such as by providing special valve lifters having internal locks which may be switched on and off either electrically or hydraulically. Such switching is conveniently performed via a hydraulic manifold that utilizes electric solenoid valves to selectively pass engine oil to the lifters upon command from an engine control module (ECM). Such a manifold is referred to in the art as a Lifter Oil Manifold Assembly (LOMA).
Prior art LOMAs are made up of several components including a cast aluminum top plate with cast and/or machined oil passages for carrying engine oil under pressure to and from the oil control valves (OCVs), a cast and/or machined aluminum valve plate for receiving the OCVs and connecting the OCVs to the oil passages, a resilient carrier member for sealing between the top plate and valve plate, a lead frame for making electrical connections to the OCVs and, of course, the OCVs themselves.
Thus, prior art LOMAs are typically complex assemblies that include a variety of parts that require individual manufacturing operations, cost, and cycle time. For example, the OCV seat is typically machined into the valve plate and the OCVs are retained in the valve plate with a snap ring. A tolerance gap between the OCV flange and the valve plate is resolved with a wave spring to retain each OCV in the seated position. This assembly works satisfactory however, requires secondary machining to the valve plate. Also, with the spring as a separate part there is a risk that an assembly is built without the spring in place, which could lead to a reciprocating movement of the OCV with the supply pressure. In such a case, the OCV would be susceptible to damage from vibration.
Furthermore, the oil supply gallery is typically integral to the top plate. Consequently, the oil supply gallery is located in the same surface as the control gallery, while it is desirable for a more efficient functionality of the LOMA to position the control path and the supply path in different surfaces.
In still another example, typical prior art LOMAs include four press-in-place metering valves that contain a small orifice in order to act as a flow limiter for engine oil passing through the LOMA. The metering valves are typically made out of zinc die-cast in a two-stage manufacturing process and contain no immediate contaminant protection that may, for example, screen out debris from the engine oil, which could damage or block the small orifice.
What is needed in the art is an improved and simplified LOMA that involves fewer parts to be assembled, that involves parts that can be easily manufactured, and that can be easily integrated into a high volume manufacturing operation.
It is a principal object of the present invention to provide an improved LOMA for controlling the hydraulic locking and unlocking of deactivatable valve lifters in an internal combustion engine, wherein the oil supply gallery is located in the gasket carrier, and wherein the OCV seats are formed separate from the cast aluminum valve plate by injection molding of a polymer.
It is a further object of the invention to provide such a LOMA wherein a simplified orifice restrictor, coupled with a strainer for keeping unwanted debris away from the orifice restrictor, is used.
It is a still further object of the invention to provide such an assembly comprising components, which may be easily fabricated, and preferably which are formed of a suitable thermoplastic polymer wherein after-cast machining of the components are kept to a minimum.